Getting straight A's on report cards is no longer possible at 20 Palm Beach County elementary schools, despite even the best student achievement.

That's because those schools are test labs for assigning pupils new "performance codes" instead of the traditional A, B, C, D and F marks. The school year's second round of report cards come out Monday.

Educators say they are trying to convince parents that the new format — including the terms "exemplary" and "proficient" — is a much better indicator of whether students are mastering state standards for reading, writing, math, science and social studies.

"The biggest obstacle is that it is such a paradigm shift because all we know are grades," said Sharon Hench, principal of H.L. Johnson Elementary in Royal Palm Beach. The school uses the new report cards in kindergarten through second grade, and the old letter grade report cards for third through fifth grades.

School district administrators say they have not decided whether to expand this experiment next year to more of the 107 elementary schools. Officials have learned it's better to take their time rolling out revolutionary changes, after their failed 2009 attempt at systemwide curriculum changes.

So far, what appears to be a small number of parents at the schools where the switch began last year have complained they miss seeing letter grades on report cards, and tests too.

Kari Hansen, mother of a second grader at Berkshire Elementary in West Palm Beach, says it's harder for her to track her child's progress without numerical scores and a corresponding grading scale.

"They are just promoting mediocrity with this new system," she said.

Berkshire Principal Maria Bishop said the school has held meetings and parent-teacher conferences to explain the performance codes. She said teachers have embraced the switch because now they can pinpoint whether students have mastered the necessary concepts for each subject at each grade level.

Letter grades, at the schools still using them, are supposed to indicate a student's "quality of work." A is for outstanding, B means very satisfactory, C is Satisfactory, D is defined as needs improvement and F is "at risk."

Educators say they worry about young children suffering mental harm or stigma from receiving an F or low marks.

Report cards without letter grades are becoming more commonplace across the nation and in Florida. Broward schools do not use letter grades in kindergarten through second grade; there's a 1, 2 and 3 numbering system instead, to indicate student performance.

Four new performance codes are used in place of letter grades at the select schools in Palm Beach County:

EX for exemplary. It is not meant to be equivalent to an A. Instead, it is awarded to a student who "demonstrates broad in-depth skill/concept development that most often exceeds grade level standards."

PR for proficient: This is the key sign, because it shows if a student "meets grade level standards."